The invention relates to a device for punching unfired sheetlike ceramic substrates, in particular so-called green sheets.
In their manufacture, green sheets must as a rule be provided with a number of small holes, which are used later for instance for through-contacting of conductors applied to the ceramic substrates. While the thickness of the green sheets is as a rule largely fixed for technological reasons, there is a need to be able to punch finer and finer holes into the green sheets.
For punching the holes into the green sheets, as a rule a punching device is provided that has a tool with a plurality of dies for punching the desired holes. The tool includes a lower tool, with a substantially flat receptacle in which the cutting holes are embodied directly or in cutting bushes. Dies whose diameter defines the diameter of the punched holes to be made are assigned to the cutting holes. Each of the cutting holes is embodied in a relatively thin wall, for instance the end wall of a bush, and lead into a chute for slugs. Here, punching waste (slugs) adhering to the face ends of the dies are blown away to the side and removed by means of compressed air.
Above the green sheets, the die protrudes through a so-called stripper bush, which prevents the part of the green sheets that adheres to the die from lifting in the return stroke of the die. While the diameter of the punched holes and thus the diameter of the dies is meant to become less, the length of the punching portion of each die is determined by the guidance length of the stripper bush and the length of the cut opening. If the die diameters are too small, the result is a tendency of the die to kink.
With this as the point of departure, it is the object of the invention to create a punching tool for green sheets with which punched openings of especially small diameter can be produced technologically reliably.